1. Field of the Invention
The present invention relates to a compression apparatus.
2. Description of the Related Art
As described in Japanese Unexamined Patent Application Publication No. H01-313694, there have been known compressors with structure for rotatively driving compressor rotors composed of a pair of male and female screw rotors by means of a motor or the like device that functions as a driving machine through a pulley with a belt, or a speed increasing or decreasing gear implemented by a combination of main and pinion gears.
In the compressors, the inside of a package is divided into two internal spaces. The internal space of a primary side houses a compressor main body, the motor for driving the screw rotors in the compressor main body through the pulley with the belt, and an oil separation and recovery unit. On the other hand, the internal space of a secondary side is equipped with a sirocco fan attached to an output shaft of the motor, an after cooler, and an oil cooler. Further, an air inlet is disposed on an outer wall of the internal space of the primary side, while a through hole for allowing air to flow from the internal space of the primary side to the internal space of the secondary side is formed in the partition wall.
To adjust a revolution speed in such a compression apparatus, the diameter of the pulley, geometry of the belt, a gear ratio, or other features must be changed (i.e. replacement work for replacing components such as the pulley, the belt, or the gear should be performed). However, the replacement work requires a certain amount of time. For this reason, it is unpractical, in the compressor of the above-described type, to frequently change service conditions of the compressor, such as specifications of an object to which compressed air is supplied.